For those times when you need something that nobody seems to have you should check McMaster-Carr.

Years ago I was doing a canoe project and looking for some specific bolts that are longer and smaller in diameter than anyone around Ann Arbor had. I Went to Grainger, Fastenal, and Stadium Hardware (everyone said try there) among others. I spent a half day trying to find the stupid things and had nothing to show for it. I was complaining to my Dad that I couldn't find them anywhere. He asked if I tried McMaster-Carr. They had a great wizard thing to select the specs of the bolt and in a few minutes they were ordered. Shipping is fast too. My last order was submitted at 3pm and with the standard ground shipping it was dropped off at my door at noon the next day. Less than 24 hours for $4.50